Party-line telephone system.



0L J. ERICKSON. PARTY LINE TELEPHONE SYSTEM.

APPLICATION FILED NOV. l5

Patented Apr. 14, 1914 2 BHEBTSSHBET l.

C. J. ERICKSON. PARTY LINE TELEPHONE SYSTEM. APPLICATION FKLED NOV.15, 1906. 1,093,041 Patented A131214, 1914.

2 SHEETS-SHEET Z.

which is shown at H.

UNITED STATE@ PATENT OFFICE.

CHARLES J. ERICKSON, OFCI-IIIICAIGi-O2 ILLINOIS', ASSIGNR. BY MESNS ASSEGNML'IS. TO FIRST TRUST AND SAVINGS BANK, TRUSTEE. 0F CHICGO. ILLINOIS.

PARTY-LINE TELEPHDNE SYSTEM.

Specication of Letters Patent.

Patented Apr. iii. it/iet.

Application led November 15. 1906. Serial No. 343.568.

To all u'zom, it may Concern Be it known that I, CHARLES J. ERICKSON, a citizen of the United States of America, and resident of Chicago, Cook county7 Illinois. have invented a certain new and useful Improvement in Party-Line Telephone Systems, of which the following is a specification.

My invention relates to telephone exchange systems employing subscriber-controlled switches for trunking or extending calling lines into connection with called lines, and in which a plurality of telephones are employed on one line, such arrangements being commonly known as extension or party-lines.

In application Serial No. 299,268 there is shown a common battery lock-out system for preventing interference between subscribers on the same extension or party-line.

An object of myl invention is to provide improved means for preventing interference between subscribelson the same line in an automatic system employing a common batteiv or centralized source of talking current.

It is also an object"to provide certain novel features and detailsr of construction and combinations tending to increase the general efficiencyv of a telephone system of this particular character.

To the foregoing and other useful ends, my invention consists in matters hereinafter disclosed and claimed.

In the accompanying drawings Figure 1 is a diagraxrrshowing two party-lines and connected through a central station. One of the said party-lines is provided with two suhstations (A and F) that are bridged across the line conductors in multiple; and the other party-line is also provided with similar substations. one of Une of said lines is shown connected through a first-selector C and a connector D with the other said party line, which latter has bridged across it a first-selector E. The substations A. F and H in Fig. l are similar, as well as the tlrstselectors C and E. A central battery B is shown having its positive terminal preferably grounded at (il. Fig. Q is a diagram of a substation K differing from the substation F only in the connections of the lock` ing relay.

The substations may be of any suitable or approved type, for instance of the general type shown in patent ayxpliration Serial No. 278.901. The substatmnf; are provided ivizh the usual details essential to snlfiscrihers stations of the dass in question. rliu; a

station A. for instance, is provided with a receiver 2 and switclrhook f5., wif li latte?Y has radiating lfrom its body a number of cam arms 4. (E and said hook vbeing plv otally secured to the keylrmrd frame (not shown) by a screw 7 about which swings when the receiver is removed. This motion is produced forT the purpose of changing eel tain switching operations to oc disclosed. l `111tlieii'xiore said sulxsta'ion has a. trans-- mittel' 9. a ringer EL an iiuluetiormfiil l* having a primary Vwinding il and a secondlary windingy l2, a condenser '1.3. impulse wheel lll which has the xiiual vertical `inipulse teeth l5 that are ada fed te. operate the vertical impulse spring; lo. In addition., T5 the impulse wheel carries a retain.' inivmeo tooth Il' which operates the rotar-v inibu spring! 18. The cam arm A contrf', called locking arm 'l'.' in #urli a man when the switehliook rises. and l; loro la dial is rotated. the ineul ung tip if() @iron the end ol' the locking can; :arm l that wf mall rests on the r'ron and oi' the smi, v 2l is driwn to the inner "te i" section of the ground ng' when the dial is rotated b v the c: scriber the pin "7 upon the end nl= ing dog is able to pass beneath ing cam to raise the said van: a trille. ca?

ing the said insulmiiig,y tip 20 to tall 'Lehi the said angled section oz ilu gremial pz-i 2l, and permitting the Vi ist* i' i fore. to make contact with a f' operati.' ground spring Q4.

The engagainent ol the gfrtunnl and E24. by the operation 1f v the. ground post in mnixerfioi: f'tli flic substation grnind (il. whereby when subscriber releases the dial after rotatai'zg u, as [.lescrilied. the vertical impulse teeth iff will cause the vertical impulse mirino' il? lo come in contact with tlirground y t '.fi; and immcdiatclv after. roturaY snpnlse tooth 17 causes the rotary impulso lWing l* to come in Contact with he saute ground post lvlienitlie switrli-hook is down the cam arn. (3 maintains the @with lspring: 2G and i?? in contant. ther-my bridging the ringer .fl in series `with tlu rondcnser' lil across ille line. 'liu` spring "2"? and 2'.) are A nus' llO then disengaged and the primary winding 11 in series with the transmitter 8 is removed from across the'line. Even after the switch-hook is raised, since the finger 30 of the cam dog 23 controls the engagement of the said springs 28 and 29, and since the said cam dog rotates in unison with the dial, if the dial is rotated the. springs 28 and 29 and, therefore, the subscribers line conductors are kept separated. The signaling device whereby a subscriber may signal another after a connection has been established comprises a push-button 31 and spring 32, which latter normally engages the Contact point 33; but when the push-button 31 is pressed, the spring 32 leaves the contact point 33 and engages the Contact point 34 which is connected to the substation ground G1. The means whereby the subscriber may release the central station apparatus brought into service comprises three springs 35, 36 and 37 commonly known as release springs, and so controlled by the cam arm 5 that when the switch-hook descends the three release springs are brought into contact, thereby grounding both sides of the subscribers line simultaneously. In addition, the substation is provided with a loci(- out relay 38 connected in parallel or shunt with the primary winding 11 of the induction-coil 10. The sulistation K shown in Fig. 2 is similar to the substations A, l1 and H. The locking relay 194, however, is shown connected in parallel or shunt with both the primary winding itl-3 and the trans mitter 196. Said relay is provided with an armature 39 pivoted at 40, and its nonpivoted end is formed into a hook bent at right angles to the armature. Said hook is adapted to engage an eye 41 on the locking dog when the lock-out relay 38 becomes energized, thereby locking the said dog in normal position; and since said dog is rigidly connected to the dial, the latter is also locked against operation by the subscriber. The armature 39 is retained in normal position by the retracting spring 42.

The first-selector switch shown at (l may be of any suitable or approved type, for instance of the general type described in Patent No. 815,321, granted March 13, 1906, to Keith, Erickson and Erickson. Among other details it embodies the following wellknown devices and circuits: The switchshat't (not shown) carries `the rotary wipers 43 and il. respectively, and the private wiper 45. well known and comprises (he side switch wipers 46, 47, 4S and 49, which may be designated as the vertical, rotary and private side switch wi pers, and the rotary inagl net wiper, respectively. The side switch is under the control of the private magnet 50.

and in the normal or first position oi the I side switch the wipers 4G, 47, 43 and h't9 ocvertical and The side switch is l .iipy the contact. points 51, 52, 53 and 54', respectively. ln the second position they rest on the contact points 55, 56, 57 and 58, respectively, and in the third position the contact points 59, 60, 61 and G2 are engaged by their respective wipers. Through the medium of the vertical line relay 63, and while the side switch. is in first position, the subscriber controls the vertical magnet 64, which latter operates to raise the switchshaft and wipers 43, 44 and 45 vertically. By means of the rotary line relay 65, and while the side switch is in first position, the subscriber controls the private magnet 50 and, therefore, the side switch. While the side switch is in second position the rotary magnet 67, which operatM the switchshaft and wipers 43, i4 and in a rotary direction. is energized. The vertical and rotary line relays and 65, acting conjointly, provide the means whereby the subscriber controls the release inagnet (3S while the side switch in [irst or second position. lt the side switch passes to third position, then, since the selector C is of the trunk-release type, the selector is controlled through the next switch, with which latter a connection is established through the private wiper 45 and by means of the bacle release relay 69. The bridge-coton' relay Y() is provided to open the connection between the line relays 63 and 65 and between said relays and battery B when the line to which the switch C belongs is called. This is desirable. because it the relays are not .lisconnccteil from each other and battery, the ringing current for signaling the sub.v scriber may operate either or both of the relays 63 and 65 and cause sonic interference with the called switch. lt is also desirable. to remove the bridge formed through the said relays from across the line, so as to give the voice-currents as clear a path as possible. The function ot' the private normal relays 7l and T2 is to control a connection between the private normal conductor 133 and `the side switch wiper tor the purpose ot removing the guarding potential at the connector l) when one subscriber is calling another bark over his own lino. By referring' to Vig. l it will be sccn that this connection is alwrliys maintained except when the relay il at normal and the relay T2 energized. .Xeross the terminals of the private normal relays Tl and T2 are bridged the condenscrs 73 and T-l, respectively, to increase the elticicnrfy ol the talking circuit. The private normal relays 7l and TQ are provided with armatures T5 and 70 and insulating bushings I7 and T8, rcspectiif'clv. to serve as; means for controlling the connections described. '.llic l donncctor switch l) may also be ol anyv suit.- l

li able or approved type, and, :is shown, is an iinliroved forni ot' the connector described in l Patent No. Sil 3,170. granted March 13, 15.106,

' to control the ringe to Keith, mricason and Erickson. The mechanical details of the selector and coLnecior, ns is well known, are very much the saine, although there is sonic material dilierrr'c in the circuits. For instaure. the oonnwior s\\'itcli-slmft (which is. notA shown) carries, like the selector, the liuc wipers 79 and H0 and the private wiper r11. The con-n nector switch also controlled by the calling subscriber through the medium of the vertical and rotary line relays t and 83. The vertical line relay SQ directly controls the vertical magnet S4 and also the rotary magnet The otiice of the vertical magnet" @i is to give ythe shaft and shaft Wipers a 'veri-tieni motion, and the rotary magnet 85 imparts to the shaft and wipers a rotary or circular motion. Thr rotary line relay S3 controls the private rnag'jfnet 86, which latter under certi-iin conditions in turn controls the vertical and rotary magnets 84 and 85, the release magnet Si', and also the side switch Wipers 8S. 953, 00, fil and 92. The side switch, like the side switch ol' the selector, has a normal or first position, a second position and u third position. The release magnet 87 also controlled by the vertieft? and rotary line relays and conjointly. By the use oi the comleuscrs 93 und 04V the connector divides', the line circuit thro into two inductifelY connected sections, Tier Lonnec* tor is provided with a difierentiallj, wound relay 95 which roniposctil of the wind-- ingr-s 06 and 97. The function oi this coil Vis r relay tif. by means of which the ringer generator 98 is bridged :u the terminals ot the c: lied line to siguai the calied subscriber aud through thel medium of which relay 9T the release man; 'net n? is controlled after the called sub-- .scribe answers. The bficlr-bridv'e relays 99 and l0() provide the called subscriber with talking battery current when his primary cir-"uit is bridged across the line. The central .station i= equipped with the busy sig?n ualinf; apparatus l of any suitabli`= design, as. for example, ilu* one mmprising :in interminer .riuiluzg; 10?, ot" the induction-coil 10?? wrote los in series with tlu` primorg" be' a busy signaling current is induced in the Seconfflarrv winding of tiw ,said inductionwoil T02. rl'lul secondary Winding litt is coiz nected with the ie Snitch Wiper 00. The fini*Peler-tor l@ ot the callwl line is, the .saine :se the first-selector and. therefore, the de scription of the selector is applicable. The substation ll, like the station F is, ot' course, a duplicate ot `substation A and, therefore, requires no desriii'ition.

FluY vullingr .operation by which the subsrrilwr i. 'for example` would call and Signal subscriber ll is as follows: To call the num ber 1:20. xvhii'h is arbitrarily chosen us the number of ille substation ll. the subscriber A at substation jill() operates his calling device in a suitable manner/corresponding to each digit. For each digit the vertical line is grounded a certain number of times corresponding to the numerical value of the digit, and then the rotary side of the line is grounded once. The receiver 2 is removed from the switch-hook 3, closing in contact the springs 28 and 29 and breaking the Contact between springs 26 and d7, thus removing the ringer 9 from across the line and bridging instead the transmitter circuit- The cam arm 4 raises the locking arm 19, as previously described. The first digit being 1 the' subscriber at substation A turns his dial for the first digit 1, thereby grounding the vertical line conductor 105 once and the rotary line conductor 106 once upon the return motion of the dial. When the dial is pulledv the pin upon the end of the locking dog S3 passes beneath the locking cam, causing the tip 20 to fall behind the angled section of the ground spring '21, as previously de scribed, thus placing the ground post Z5 in connection with the substation ground G1. Grounding the vertical line conductor 105 onoe energizes the vertical line relay 0:. of the tirstselector. The circuit through said vertical line relay extends from grouu'fl G* through the ground springs 21 and 24 i.. the ground post Q5, thence to the verticni un pulse spring 16, vertical line conductor "05 to the side switch wiper 46, Contact point 51, through the vertical'line relay fifi to the bridgecut-otf springs 106 and 107 (the bridgocuboff springs being normally in contact) to the battery lead 108, thence through battery B to ground Gr.

Each time that the vertical line relay ($3 is energized the vertical'line relay springs 109 and 110 are pressed into contact and Lin energizing circuit is each time established through the vertical magnet 64. The circuit through said magnet extends from ground G2 to the relay springs 110 and 109, to the private magnet springs 111 and 112, through the winding of the vertical magnet 64 to tht` battery lead 105%, thence through battery ll :o ground The vertical magnet 64 beingr ,w1-awt once, the first-selector switch-shaft nul u ipt-is Yt. i4 and 45 are raised one ste'y 'l lic said wipers are carried to a level Wlti the contact points that constitute the terminal of thc trunk line leading to the connector su'ilrn l). Followingr the vertical impulso the rotary impulse spring 18 is grounded once by the rotary impulse tooth 1.7. thereby grounding the rotary line conductor 100 once and energizing the rotary line relay 65. The path of this energizing circuit is from grr und G1 through the `Qround springs Q1 an Q4 to the ground posg Q5, rotary impulse spfing 18 to the rotary inc conductor 100, sido switch wiper 47, Contact point 52 to the rotary line relay 65, thence to the bridgecut-olt springs 113, 106 and 107 to the battery lead 108, thence through battery B and to ground G. The rotary line relay upon energizing presses the line relay springs 114 and 110 into contact, thereby closmg an energizing circuit through the private magnet 50. The current through said magnet passes from ground G2 through the springs 110 and 114 to the private magnet 50 and battery lead 10S, thence through battery B and to ground (il. The private magnet being energized for a moment the side switch of the first-selector passes to second position, permitting the side switch wiper 49 to close the energizingr circuit through the rotary magnet G7. The current flows from ground G3 through contact point 58, side .switch wiper 49 to the interruptor springs 115 and 116, thence through the winding of the rotary magnet G7 tothe battery lead 10S, thence through battery Band to ground G. The rotary nnignet is energized one step and the shaft wipers 43, #te and 45 are carriedjnto engagement with the bank contacts that constitute the terminal of a trunk line leading to the connector' switch D. lf the first trunk line is busy an energizing circuit/is established tl'irough the private magnet 50, when the private wiper 45 strikes a grounded contact, thereby retaining the side switch in second position and maintaining the circuit through the rotary magnet G7. The rotary kmagnet by intermittent niagi'ietization causes the shaft wipers to rotate past the last busy trunk line. However, as soon the private magnet deiincrgizes the side switch is tripped into third position. or it there are no busy contacts to be passed over, the rotary magnet 0T. as is well known, trips the side switch to third position, when the wipers engage the first trunk line, with the result that as soon as the side switch wipers 46 and 47 rngage their respective contacts 59 and 60, the subscriliiefs line isextcnded to the connector switch l). Also, since the side switch wiper 1S engages the grounded contact point 0l, a guarding potential is established at the private wiper 15 for protecting the seized trunk line at the connector l) from being molested by any other su itch. This guarding potential also protects the callingl line by establishing a guarding potential at the connector bank over the private normal conductor 11T. The secontl digit is called after ilu` subscriber' has established connection with the connector D by way of the trunk conductors 11S and 119. The subscriber rotales the dial. as descrilwd, for the second digitI L", thereby grounding the vertical and rotary lin(` tufnductors 105 and 10G which causes tlu f-iuxrgiL/ation ot' the connet'tor ver-y line relays and 83, and.

tical and rotary also of the diti'crential relay 05. The ener; gizing current [lows over the follmving path: Ytrom ground G1 to the vertical line conduttor 105, to the side switch wiper L16, Contact point 59, through the winding of the private normal relay 71, shaft wiper 43 to the trunk conductor 11S, through the winding of the vertical line relay 82 and winding 90 of the differential coil 95 to the battery lead 108. thence through battery B to ground G. Each time the vertical line relay 82 is energized the line relay springs 123 and 124 are pressed into Contact and an energizing cir cuit is each time established through the vertical magnet The energizing of the dit` ferential relay is of no consequence at this time. The energizing current through the vertical magnet 84 Vfiows from ground ti to the springs 123 and 121, private magnet springs 125 and 126 to the vertical magnet contact point 12T, side switch wiper to the battery lead 108, thence through battery B to ground G.

Each time that the vertical magnet 84 is energized it raises the shaft. and wipers T9, and 81 one step at a time until the said wipers are carried two steps to a level in which are located the terminal contacts of the line #120. When the rot ary line corn ductor 106 is grounded the rotary line relay 83 and the diiferential relay 95 become en crgized through the following path: from ground G1 to the rotary line conductor 100, side switch wiper 47, contact point '30, through the winding of the pri vate normal relay 72, shaft viper .4t-4, trunk conductor 119, through the winding ot' the. rotary l"A i relay 83 and winding 97 of the ditlerentia relay to the ringer relay springs 120 anni 121 (which are normally in Contact), and to battery lead 103, thence through battery .il and to ground G. The energization of the rotary line relay 83 causes the springs 12S and 123 to come into contact, thereby com pleting a circuit through the private iii-.val net 8G. The path of the energizing circuit is from ground Gt, line relay springs 123 and 128, through the winding of the private magnet 86 to the ringer relay springs 120 and 121, to the battery lead 108, then@ through battery B and to ground G. The momentary energization of the private niagnet- 8() causes thel release ot' the side switch from tirst to second position, thus placing thev side switch wipers and S0 in contact with the points 129 and 130, respectively. The last digit. heilig' 0 the subscriber op erates the dial, as };reviously described. grounding the vertical line conductml 10.3 ten times and the rotary line conducto;- 20u once. The vertical and rotary line rela) s S2 and S3 are operated over the previeusly traced circuits. However, when the line relay springs 123 and 121 engage, a circuit is closed through the rotary magnet 8.7 instead of through the verticalimagnet S4. The cir' cuit 'may be traced from ground Gr4 to the line relay springs 123 and 124, through springs and,126, through the rotar);

1: 'Si'. minar! point 129, side switch to the batteur lead 108. thence irattfrv i); ii'i'gnonnd (fr Fach time magro-i. energized the ro- :eiture is atti.J ,ieri and rotates the wipers '71?, 80 and 81 one 'fi the said wipers are rar- '-fnr ith the normal conthat lead to the *,i .subscriber Whose number riiergrization of the rotary line eviousy Stated, completes an rircuit through the private mag' 1.5i; now operates `with one of two :i onely tile reiease of the side switch *n ,zaini position, or the so r Mee cf the ennnentor, which eiupprse the `former reiie eine switch to pass to side switch in Contact with 11"( and 138, ren eircnit through inetliatdy estabnpraft point 135, v ringer relay 97', reta); springs 139 .ut 1114, side switch iced S, thence ground G. The wenn? :y 57 extends 1% no .fio or' the callthe 'Furthennorm o iiircl positien ti for the i Tiisgmrding r/jianid G to the side private contact ot' the inn; gmiriniai "t more. causes tin bridge mate con -i2ictf r 133,

und Lgf 111.7 io the to t ilo ba t tcry 51, ground G. to separate tin? i Tilrl l'liyilrfff llic caiii i" ouri the line i I for this eircuit passes lay were not energized, ringing rurrent would pass out over the called subscribers line conductors 131 and 1327 since the vertical and rotary side switch wipers 91 and 92 are then directly connected with the line wipers'79 and 80, respectively. It is' for this reason that special provision has been made for the ringer relay springs 111 and 142, to separate them from the ringer relay springs 143 and 144 at the instant that the side switch passes into third position. Furthermore, when the vertical line relay 82 hecolnes energized the differential relay is also energized through the winding 16. The armature is attracted and the sprin s 14() and 139 are separated, thereby brea ing the continuity of the energizing circuit throu h the ringer relay 97'; and as a result tie ringer relay becomes denergized, thus allowing the springs 141 and 142 to fall back into contact with the ringer generator springs 143 and 1411, respectively. As a result, ringing current is then permitted to pass out on the line of the called sub seriber, which current passes through his ringer and signals hiui. This signaling cur rent passes from the generator J to the springs 143 and 141. side switch wiper 91. contact point 13T. shaft wiper T9, normal conductor 131, vertical line conductor 1715, condenser 146, ringer 14T, springs 148 and 149 to the rotary line conductor 150, non mul coi'iductor 132, shaft Wiper 80, contact point 138. Aside switch Wiper 92, ringer relay springs 142 and 144 and back to the generator J. As soon as the calling suiu scriber releases his signaling button the current through the diferential relay 59.) is interrupted, denergizing the differential relay, The springs 139 and 110, upon reengaging, reestablish the energizing circuit through the ringer relay 97', which latter .spon attracting its armature severs the conf Vtion between the generator J and the na-1d line. Asrthe called subscriber rei mom his receiver 168 from the switch-hook 170 the latter, upon rising, destroys the ringing circuit through the bell 147 at the in etant the springs 148 and 149 separate` The i mitch-1100i( also forces the primar,l circuit l prings 151 and 152 into contact, closing a circuit through its own station that pr0- tides the transmitter 153 and the primary winding 154 of the induction-Coil 155 with i :,urrent for talking pur ones. The current tiem ground G to i :lac side switchfwiper 89. to 4the coil 100. i ringer relay springs 157 and 142 to the side switch wiper 92, rotary line wiper 80, coni limtorrA 122 and 150. primary winding 154 i of the indl1ction-coil 155, transmitter 153, l springs 152 and 151 to the vertical line coni durtor 1451` conductor 131, vertical line wi er i 71), side switch' wiper 91 ringer reina? i epriuge 14:1 and 159 to the bark-bridge coil 99, thence to the battery lead 108, and through battery B to ground G.

It will be noticed by referring to the drawing that the lock-out relay 171 is connccted in parallel or shunt with the primary winding 154 of the induction-coil 155; hence when current Hows in the primary winding 154 a part is shuntcd through said relay, thus energizing the lock-out relay which attracts its armature 172` which latter in turn engages the locking dog 173, thus rendering the calling device inoperative. The onergizing current for the talking circuit, in passing through the coil 100. energizes said coil and causes thc armature to close in contact with the springs 160 and 161. At the instant these two springs 160 and 161 engage, the calling substation provided with current for energizing or charging the talking apparatus. The circuit in this case eX- tends from ground G5 to the side lswitch wiper 89, to the relay springs 160 and 161, ringer relay springs 162 and 120, through the winding 97 of the differential relay 95, rotary line relay 83., conductor 119, firstselector shaft wiper 44, relay T2, side switch wiper 47 to the rotary line conductor 106, primary winding 11 of the induction-coil 10, transmitter 8, springs 29 and 28 to the vertical line conductor 105, side switch wiper 46 to the-private normal relay 7l, shaft wiper 43, conductor 118, vertical line relay 82, through the winding 96 of the differential relay 95, thence to the battery lead 108 and through battery B to ground G. Since the lock-out relay 38 is placed 'around the primary winding 11, the said relay becomes energized and attracts its armature 39 and locks the calling device of the substation #110 while ycurrent is flowing in the above circuit.

lt will he noticed that the two windings 96 and 97 ot the diil'erential relay 95 are included in the circuit. that provides the callingr subscriber with talking current. These two windings are so arranged that when the current passes through them in this manner the differential relay 95 does not energize. Since the talking circuit current to the calling subscriber passes through the vertical and rotary line relays S2 and 83, as soon as the said circuit is established, these two relays become energized and attract their respective armatures. thereby placing the release springs 156 and 163 in contact. This would result in the release of the connector were it not for thel tact that the ciamection between the release magnet S7 and the nongrounded battery terminal is interrupted between the ringer relay springs 1:20 and 121. while the ringer relay 97 is energized. Furthermore, the private normal relays 71 and 7i'l of the first-selector become energized, placing the springs 164 and 165 in contact and separatingthe springs 166 and 167.' This,

however, in no way removes the guarding potential established at the connector bank for the protection of the calling line. Under these conditions the primary windings 11 and 1.34 of the substations #110 and #120, respectively. arc connected in snies in a circuit shown in heavy lines in Fig. 1, through the condensers 73, 03. 94 and 74. The receivers Q aud 168 of the two substations in question are in series, each in a local circuit with their respective secondary windings 12 and 169 of their induction-coils 10 and 155, and in a well-known and familiar manner the two subscribers may communicate with cach other. since their primary circuits are charged with a suitable current from the central or common battery B.

An intruding subscriber is prevented from interfering with or molesting an established connection. Suppose the subscribers A and H are in connection over the circuit previously described, and theI subscriber F (who occupies the line in common with A) removes his receiver 15S from the 'switch-hook 174. thereby bridging his primary circuit inchiding-the primary winding 175' and transmitter 176 across the liuc. lmnicdiatcly, thc lock-out relay 177 becomes energized,attracting itsv armature 178.which latter engages the lockingr dog 179, thereby rendering the calling device at substation .F completely inoperative both `t'or switching and signaling purposes. The substation locking dog is prevented from turning, and from connecting the substation ground release spring and signaling button and ground post through the ground springs. Therefore, the subscriber F can in no possible manner interfere to disconnect or destroy the established connection. The subscriber l upon hanging up his rcccivcr 15.5` removes the primary winding 175i from across thc linc; consequently the lock-out relay 177 becomes dcncrgizcd and the armature 17S and the locking doo 179 disengage, whereby the substation F becomes operative when the established connection is destroyed.

The front rclcasc occurs when the calling subscriber restores his receiver 2 to the switch-hook 3 thereby pressingr the release springs 35, 36 and 37 into engagement, which engagement places the line conductors 1.05 and 106 in connection with the substation ground (il. The grounding of the rotary linc conductor 106 produces a cessation `of the flow of current though the rotary line relay SiS-and the windingr 97 of the differential relay 05. This brought about by short-circuiting those two windings in series through ground. The shortcircuit extends from ground G1 to the rotary line conductor 106. side switch wiper 47,4coniact point 60. winding ot thc relay 72, shaft wiper 44, truuk conductor 119 to the rotary line relay 83. winding 97 of the dit erential relay 95 to the ringer relay springs lil) and 162. springs ll and 16() to th a siale switch wiper 8S) and to ground G". The rotary line relay becomes deelnergizell and the trunk release spring 16B reeetlea from the springr 15G. and since only the winding 9G of the differential relay 95 is rereiring current the said relay beoomes energized. The current-flow through the said relay e tends from ground Gf1 to the release spring;` $57. 3G and 35. to the vertical line conductor 105, side switch wiper #113. Contact point 59. through the winding of relay 71, shaft wiper 43. trunk ronductor 118. vertiaal line, relay 82. winding -96 of the ditl'erenial rehij.Y Jo l to the battery lead 108. then through hat` terv VB to ground G.

The energization of the differential relay 95. as above. produces a. denergaation of the ringer relay 97. which latter upon restoring its armature to normal position permits the ringer relay springs 162 and 1Q() to disengage and the spring 120 to come in contant with the spring 121. The engagement of the springs 120 and 121 again Completesv an energizing cirrnit, through tbe winding: 97 of the diercntial relay 9.3. and current in this way passes through said winding. in auch a direction as to reinforce the winfihrt 96. T horefore. even after the ringer relay becomes denergzed the dil'erential rela): continues to remain magnetized as long as the release .springs 35. 36 and 37 remain in contact. The magnetizing current through the winding 97 of the differential relai7 95 passes from ground Grito the rotary line conductor 106. through the relay 72 to the rotary line relay 83, Awinding' Q7 to the ringer relay springs l2() and 1:21. to the battery lem/l 108, thence through battery B and to ground G. Furthenmore, at the instant that the said ringer relay springs resume their nor mal position, and simultaneously with the renergization of the rotary line relay S3 of the connector. the trunk release springs 156 and 163 engage, thus completing an energia 'mg circuit through the release magnet S7 of the connector and the back-release relay 65) of the fil'steelector, releasing said switrlies and thus restoring them to normal position and in readiness for further use.

The ener rgization of the back release relay 6U of the first-selector causes the springs 183 anrl l to engage, thereby completing:v an energize.4 ing circuit through the release magnet` (i8. It iS evident that as soon as the Connector Wiper 81 is removed from the point with l which it has been in engagement. the briflgel v cutoff relay '7'0" of the rstseleotor li resumes its normal position, leaving the first l selector in condition to be operated by the l inbotaton #120. At the saine time that l the rivate wiper 81 leaves Contact point l G5 tlm` inenwiners 79 11H80 alao leave their l 'viously been rotate-,l omo a wi per 47, rotarq line coluluctoi llt. hrinia Contact points; and as a result the circuit conveying talking current to the sobatation #.120 is also destroyed, at the same. tune raming the deiiaergiaation of the reiay 10G :intl the separation oi they nprings and o llil. therein" interrupting the Circuit through wliirh current tloxrs through substation, #11() for talking purposes.

lt has been found in practice that good results 'are obtained when the suhstatirm re lays 38, 177 and 171 are wound to a re sistanoe, of live hundred ohms. each.

The busy release 'follows as a result ol' the emirgizing of the rotary line relay nii. if the Called line, is busy. as folletti.. The said ref lay 83. upon energizing. energizes the pri vate magnet 86, as previously stated. which latter in turn presses the springs i and 181 into Contact. As soon as the said springs engage, the release magnet 87 is then placed in Connection with the private Wiper 81 (since the sitle switch Wiper 89 is now in second position and in engagement with the notant point 130i. uhu-h wiper heul. gire tart, As a result a. tlf; through the release was from the gr ed Wiper 81 to that atie eli/heh wiper Sr. Contact point 151i. mirate magnet apriigs 181 and 130 to the r t 5T. ring.; relav Springs lil and '3,151 to the. hattet lean 108. theatre. through battery 15% and te ground G. t ergizing releases the eonmartor swilrlwisait and restores the ronnector siffle :writ i first ponition, retilrnirg'g the 'vertical ma to the control ot the wrtifrtl lint- '2. Thrrefl'ire. now th seriher grounds the rerii'sal Q 1105 to signal. instead of ri f maar lef rel' he operates the vertical. wi h latter in turn lpetafff the busy maeliine T 'through the siilr swihh fl L5 k wiper 90. to the Contact point lil/fl. -prinj i815', Condenser 911. oonnertor irunlt onu dut-tor 119. tirstfselwttor shaft wiper 4l. um

denser 74. Contact point (it). :fuir witwinding7 l' of the indnrtioircl'ni @i trai' mittcr 8. contant point 3?, sprint; .,fl to me .springs Q9 and vertical line oondu r 105, side switch wiper "i6, :tonta t point .W to thel oondenser 73, first: ufeleutor ahah, w.. 43, connector trunk eox'aluftor 118. mi; looser 93. haeklirillge relay 99 to the l y tery learl 108. thenmto the husy inat'hire i. The calling suheorilnfr upon hvaring the busy signal widerstand that the desire@ llt line is in service and will release the switching apparatus by' hanging up his receiver.

To call any subscriber not on his 0WD line the culling subscriber will bring about the opcrationpas described in the preceding; but a subiscriber like subscriber at substation il may also call another subscriber' on his own line. For instance, suppose the subscriber A desires to signal a subscriber occupying the same line, as at F. In this case the. calling and called lines are identical, but special provision is made in the .-rstscicctor switch to momentarily remove the guarding potential established at the fzfmfnector bank, and thus allow a subscriber to will back on his own line.. W'hen the last rotary impulse is sent over the line the private nbrmal relay 72 becomes energized; thus the springs 166 and 167 disengage and remove the guarding potential from they connector bank. Therefore, this impulse to the rotary line removes the potential which would cause the busy release of the connector, providing the guarding potential still existed, and sends the connector side switch to 'third position. It is evident, therefore, that a subscriber calling another subscriber on his own line would never get a busy release., The subscriber A having connected the switching apparatus at the central station with his own line, then by pressing the signaling button a suitable number of times sends signaling current impulses out on his line, ringing the different substation bells which are bridged across the called line. The subscriber at F recognizes his substation signal (two rings, for instance) and removes his receiver from the switch-hook. The energization of the relays which places talking current on the circuit is brought about by the substation A at the instant the primary circuit is bridged across the line after the call is completed and, therefore, when the dial returns to nor# f mal and closes the springs 282and 29, after the last rotary impulse has been sent in. Thus it will be seen that any subscriber may call his own line, inasmuch as the connector switch D used in this case will not be automatically released as soon as it engages the multiple line terminal connected with the line from which the call comes. Furthermore, it' one subscriber on a party line is using theline no other subscriber on the same line can use the line for either signaling or switching purposes. In otheriV nerds, the two subscribers who are conversing over the line are safe from intrusion or molestation to this extent, namely thai no other subscriber "can use the line for switching or signaling purposes, nor can any other subscriber on the same line so operate his telephone ,for calling device as to endanger the contin/uity of the circuit established between the t'wo subscribers who are talking. It. is always undesirable, of course, to have it possible for one subscriber on a line to lstenein and hear the conversation conducted over the line by some other subscriber', but in an automatic or semi-au toniatic system I deem it of fargreater importance. to provide against the breaking by a third subscriber of a circuit already established between two other subscribers; for while such listening-in may be a source of more or less annoyance. it is evident that this is not so important a consideration as is the maintenance of an established talking circuit. Subscribers may tolerate listening-in, objectionable though it is, but

'any situation in which a party-line subscriber could not use his telephone without guarantee against interference on the part of other .subscribers on the line would not be tolerated. It is evident, however, that my improved lock-out arrangement and devices are of a character to prevent the subscriber from transmitting any signal and from accomplishing the closure of any circuits at the central station.

As indicated in Fig. 1, when the subscriber #110 wishes to call the subscriber F on his own line, the connector D makes connection with the contact points 79', 80 and 81. The normal conductors 131 and 132 lead `back to the line of the calling subscriber, so that when the connectorcompletes the connection it is connected back with the calling line. It will be clear, however, that the guarding potential placed at the connector private bank contact 81', when the selector C first comes into use, is removed when the calling subscriber grounds the rotary line conductor 106. Grounding the rotary line conductor 106, it has been explained, energizes the rotary line relay 83 of the connector D through the private normal relay 72 of the selector C; and, as a result, when the said relay energizes, the springs 166 and 167 are separated, `and the guarding potential to the private normal conductor 133 from ground Gr6 is removed to permit the connector side switch to pass to third position. When the subscriber #110 connects with the subscriber H of a different line, the talking current for` the substation A passes through both private normal relays 71 and 72, and both of said relays pull up simultaneously; but in that even't'the guarding potential is not removed, since the circuit destroyed between the springs 166 and 167 by the relay 72 is restored at a point between the springs 164 and 165 by the relay 71. The saine is true of the said relays when the subscriber A calls the subscriber F; but this does not occur until after the connector side switch passes to third position, so that there is no interference from such operation.

With reference to the energizing circuit for the substation relay, it will be evident that said relay may be connected in shunt or parallel with the primary winding of the induction coil, as the relay 38 is shown connected in Fig. 1, or it may ybe in shunt of both the primary winding and the trans mitter, as shown in Fig. 2, in which the relay 191i is connected in shunt with both the winding 195 and the transmitter 196.`

Vith such a connection the substation relay 194 would receive a stronger energizing current. In either case, however, the relay is in the main line circuit, but not in the talkingr or voice-current circuit. The cons nectois, and also the second and third se.- lectors if any, can be employed on a percentage basis, and may thus be less in number than the subscribers. rPhe lirst-selectors can also be reduced to a percentage basis in anyvsuitable or known manner. In this way automatic trunking is afforded between lines using common battery transmitters and dial locks for preventing:r interference lbetween partyline subscribers on the same line.

lVhat I claim as my invention is:-l

1. In a telephone exchange system, the combination of automatic means for trunking between calling and called subscribers, a telephone line, a plurality of calling dials on said line, a common battery for furnishing switching and talking current to said line, means for lbridging the battery across the line, a locking magnet for each dial, and means for preventing,r bridging of the battery across the said telephone line until after theI line calls or is called, said magnets bridged across the line.

2. A subscribers calling dial, a telephone line, a dial-locking magnet bridged across the line, a. commoli battery, means for bridging said battery across the line to energizesaid magnet, and impulsetransmittinar means responsive to the operation of said dial.

B. A subscriber-s callingr dial, a. telephon line, a telephone bridged across the line, a dial-loekin`r magnet bridged across the line.l a common battery, means for bridging said battery across the lille to charge the telephone andencrgize. said magnet, and impulse-transmitting means responsive to the operation of said dial.

4. A subseribers telephone, a calling dial aoeiated with said telephone, a telephone circuit. a dial-locking magnet, subject to control by other subscribers, connected in a parallel branch or shunt of said circuit, aud impulse-transmitting means responsive to the, operation ot' said dial.

5. subserihers rotatalllf` calling dial, an iwlaclion coil. a diallocking magnet connected in shunt or parallel with a winding ol said coil, and impulse-transmi(ting means responsive, to the operation ot said dial.

6. A subscribers rotatable calling dial, an induction-coil, a dial-lookin magnet connected in shunt or parallel With the primary winding of said coil, and impulsetransmitting means responsive to the operation ,of said dial.

7. A subscribers rotatable calling dial, an induction-coil, a telephone transmitter connector in series with the primary of said coil, a dial-locking magnet connected inparallel or shunt. with the said transmitter and primary, and impulse-transmitting means responsive to the operation of saiddial.

8. A subscribers rotatable calling dia-l, an inductioincoil, a dial-locking magnet connected in shuiyt or parallel with a winding of said coil, a common battery or centralized source ot' talking current for energizing said magnet, and impulse transmitting means responsive to the operation of said dial.

l). A snbscribers rotatable calling dial, an induction -coil, a diallocking magnet con,- nected in shunt or parallel with the primary winding of said coil, a common battery or centralized source of talking current for energizing said tpagnet, and impulSe-transmittingr means responsive to the operation of said dial.

10. A subscribers rotatable calling dial,

an induction-coil, a telephone transmitter connected in series with the primary of said coil, a dial-locking magnet connected in parallel or shunt withy the said transmitter and primary, a common battery or centralized Source of talking current for energizing said magnet, and impul'se-transmitting means re sponsive to the oppration of said dial.-

11. A subscribers calling mechanism, an induction-coil, a lock-out magnet connected in shunt or parallel with a winding ot' said coil, subject to control by other sul'iseribers, and impulse-transmitting means responsive to the operation of said mechanism.

' 12. A subscriber-s calling mechanism, an inductioncoil, a ,lock-out magnet connected in shunt or parallel with the primary winding of said coil, subject to control by other subscribers, and impulsetransmitting means. responsive to the operation of Said mecha.1 msm.

induction-coil, a. telephone transmitter conneeted iii/series with the .primary of said coil', a lockout magnet connected in parallel or shunt with the said transmitter and primary, subject to control by other subscribers, and impulse-transmitting means responsive to the operation of said mechanism.'

14. ln a telephone exchange system, the combination of automatic means having vertical and rotary motion for trunking between calling andralled subscribers, a telephone line, a. plurality ot calling dials on .said line` a'eommon battery for furnishingr switching and talking current to said line,

13. A subscribers callin r mechanism an means for bridging the `battery across the line, aA locking magnet foreach dial, and means for preventing Abridging of the battery across the said telephone line until after the /line calls or i: calledfsaid magnets bridged' across .the lne.

tical motion and finding lines by rotary motion, and means for bridging said battery across the line to charge the telephone and energize said magnet.

17. In. a telephone system divided into groups, a 'subscribers telephone, a calling dial associated with said telephone, a' telephone circuit, means responsive to .said dial for selecting groups by vert-ical motion and finding lines by rotary motion, and a diallocking' magnet connected in a. parallel vbranch or lshunt of said circuit.

18. In a telephone system divided into groups, a subscribers rotatable calling dial,

` means responsive to said dial for selecting groups by vertical motion and finding lines by rotary motion, an induction-coil, and a dial-locking magnet connected in shunt or parallel with a winding of said coil.

A 19. In a telephone system divided into groups, a sufbscribers rotatable calling dial, means responsive Ato said dial for selecting groups by vertical motion and finding lines by rotary motion, an induction-coil, and a dial-locking magnet connected'in shunt or parallel with the primary winding of said coil..

20. In a telephone system divided into groups, a subscribers rotatable calling dial,

means responsive to said dial forselecting groups by vertical motion and finding linesl by rotary motion, an induction-coil, a tellephone transmitter connected' in series with the primary of said coil, and a dial-lockingJ magnet connected in parallel or shunt with the said transmitter and primary.

2l. In a telephone system divided '2 into groups, a subscribers rotatable calling dial, an induction-coil, a dial-locking magnet connected in shunt or parallel with a winding' of said coil, means responsive-to said dia-l for' selecting groups by vert-ical motion and finding lines by rotary motion, and a common battery or centralized source of talking current for energizing said magnet.

22. In a. telephone system divided into groups, a subscribers rotatable calling dial,

an induction-coil, a 'al-locking magnet oon- 'nected in shunt or parallel with the primary winding of said coil, means responsive to said dial for selecting groups. by vertical motion and nding lines by rotary motion, and a common battery o r centralized source of talking current .for energizing said magnet.

23. In a telephone system divided into groups, a subscrbers rotatable calling dial,

an induction-coil, a telephone transmitter connected in series with the primary of said coil, a dial-locking magnet connected in parallel or Yshunt with the said transmitter and primary, means responsive to said dial for selecting groups by vertical mot-ion and linding lines by rotary motion, anda common battery or centralized source of Ytalking current for energizing said magnet.

24. In a. telephone system divided into groups, a su'bscrifbers calling mechanism, mennslresponsive to said mechanism for selecting groups by verticalun'otion and linding lines by rotary motion, an inductioncoil, and a lock-out magnet connectedin shunt or parallelwith afwinding of said coil.

'25. In a telephone system divided into groups, a subscribers calling mechanism, l

means responsive to said mechanism for selecting groups by vertical motion andfinding lines by rota-ry mot-ion, an inductioncoil, and fa lock-out magnet connected .in

.shunt or'parallel with the primary Winding of saidicil. Y y y 26. In -a telephone system divided into groups, al suibscribers calling mechanism, means responsive to said mechanismfor selecting groups by vertical motion and {inding lines by rotary motion, an inductioncoil, a telephone transmitter connected in series with-.the primary of said coil, and a lock-out magnet connected in" parallel or shuntI with the said transmitter and primary.

Signed by me at Chicago, Cook county,

Illinois this 9th day of November, 1906.

CHARLES J. ERICKSON.

Witnesses:

EDWARD D. FALES, H. J. GU'rrMAN. 

